B. Subgroups
<span>When constructing a dichotomous key, the first step is to look at the group of objects or organisms and separate them into two groups based on a single distinguishing characteristic. Then continue to separate each of the groups until each object has its own separate set of characteristics.</span>
Answer:
Superposition
Explanation:
Sedimentary rocks are deposited one on top of another. The youngest layers are found at the top of the sequence, and the oldest layers are found at the bottom.
metals (left side of periodic table) become positive ions so calcium would be the answer
